Tracing the geographical origin of wines using Sr-isotope as crucial geochemical tracer

The Department of Earth Sciences of the University of Firenze has been involved in the research project ISSUOVINO with the aim to define a geochemical marker suitable to associate the wine to its grape harvest terroir. Following this research guideline, we have determined Sr isotope ratios (87Sr/86Sr) in a number of microvinifications on single grapevines belonging to the "Azienda Barone Ricasoli S.p.A." at Brolio, and, in order to make a comparison, in other high-quality wines of the Italian territory, namely: other wines of the Chianti Classico Consortium (Tuscany) along with wines of the Cesanese (Latium), Aglianico del Sannio (Campania), and Aglianico del Vulture (Basilicata) Consortia. The 87Sr/86Sr measurements on wines have been normalised to the 87Sr/86Sr of sea-water, resulting in the definition of a parameter called Indice di Provenienza Controllata (IPC). Wines of each farm have distinct IPC values that can be related to the lithologies of the geological substratum underneath each vineyard. The vineyards of the Chianti Classico Consortium are located on geological substrata belonging to both Pliocene marine sediments and Tertiary Carbonate Flysch (-1.6< IPC <-0.2), and Oligo-Miocene sandstones and pelites of the Tuscan Nappe (IPC >2.0). The vineyards of the Cesanese, Aglianico del Sannio, and Aglianico del Vulture Consortia are mainly located on Pleistocene volcanic deposits with IPC values from +0.5 to -2.0. In the context of the microvinifications of the Azienda Barone Ricasoli, we have collected grapes in 11 sampling points, for a total of 62 analyses, during the 2008 and 2009 grape harvest. The results demonstrate an excellent reproducibility of the IPC values of each sampling point in the two harvesting years. This suggests that the Sr uptake process from the grapevine roots to its final product, the wine, is time independent. Another result obtained during the pilot study is related to the small-scale, albeit detectable, variability of IPC values observed among the different sampling points. This variability is due to both the heterogeneity of the geological substratum of the vineyard, and the isotopic change of the leachable Sr fraction, hence bio-available, from the soil. These small-scale IPC value differences can allow to further select the cultivation suitability of single cru apt to yield wines of the best quality. In conclusion, the results obtained during the research project ISSUOVINO led to the definition of the extremely promising isotope-geochemical tracer called Indice di Provenienza Controllata. Wines inherit their inorganic element inventory from the geological substratum on which each vineyard is embedded, hence the IPC value can safely represents a meaningful parameter in the analysis procedure to guarantee the geographic origin and the production terroir of wines. It is noteworthy that the certificate of guarantee of geographic origin of products of the agricoltural food chain has been recently established in the law issued on January 2011 by the Agricolture Committee of the Italian Camera dei Deputati.